Power driven toothbrushes are very popular today. The best known type resembles a common manual toothbrush, except that the brush head is vibrated or longitudinally reciprocated against the user's teeth. Although such power brushes simplify brushing of the teeth, to the extent that the amount of manual manipulation of the toothbrush is reduced, the quality of the cleaning of the teeth is not improved, nor is the massaging of the gums.
It has long been recognized that previously unattainable dental cleaning benefits can be achieved with a toothbrush that has twin rotary brushes which straddle the teeth and reciprocate angularly in unison. For example, in U.S. Pat. No. 4,048,690, issued to Wolfson on Sep. 20, 1977, a toothbrush is disclosed which includes such rotary brushes, as well as an upwardly directed and a downwardly directed stationary brush between the rotary brushes. This toothbrush has the advantage of being able to clean both surfaces of both rows of teeth and the biting edges simultaneously. Since the toothbrush is powered, rotary brushes are particularly effective at abradably removing plaque and sweeping it away. However, the stationary brushes, which clean the biting surfaces of the teeth can be utilized only by moving the entire toothbrush and, in this sense, the toothbrush is no better than a manual toothbrush. Also, the construction of this toothbrush proved to be too large and bulky to fit and operationally function within the mouths of persons have average or small mandibles.
U.S. Pat. No. 3,732,589, issued to Burki on May 15, 1973 discloses a powered rotary toothbrush in which radially directed bristles are provided between twin rotary brushes. Although this results in a reduced size and produces some power cleaning of the biting surfaces of the teeth, the rotary action of the radially directed bristles is not particularly effective in cleaning the biting surfaces of the teeth. Manual movement of the toothbrush is still necessary.
U.S. Pat. No. 4,766,630, issued to Hegemann on Aug. 30, 1988 discloses a powered toothbrush which includes a pair of longitudinally extending, reciprocal stroke arms extending between the rotary brushes and disposed above and below their axis of rotation, respectively. The stroke arms are secured, by axially directed pins between the rotary brushes, and the portion of the upper arm between the rotary brushes includes upwardly directed bristles, while the portion of the lower stroke arm includes downwardly directed bristles. When the stroke arms are oppositely reciprocated, reciprocated, annular movement of the rotary brushes is achieved. At the same time, the bristles on the stroke arm achieve reciprocal linear movement. For the first time, it was possible to achieve effective power cleaning of both surfaces and the biting edges of both rows of teeth simultaneously. However, the need to use the dual reciprocal arms made the body of the brush too bulky and interfered with convenient use of the brush.
The need exists for a toothbrush which has both longitudinally and rotary reciprocating brushes to effectively clean the teeth and gums, but which is composed of relatively few components and is sufficiently small so that even users with smaller mandibles and mouths can use it without discomfort.
In accordance with a preferred embodiment of the present invention, a powered toothbrush is provided with a pair of disc-like rotary brushes mounted for rotation about a axis generally perpendicular to the length of the brush. The rotary brushes are in axially spaced relationship and are provided with inwardly directed bristles. Between the rotary brushes, upper and lower linear brushes are mounted above and below the axis of rotation for linear reciprocating motion generally perpendicular to that axis. The upper brush has upwardly directed bristles, and the lower brush has downwardly directed bristles, and the linear brushes are mounted to the rotary brushes so as to be brought into reciprocal, linear movement when the rotary brushes are reciprocated angularly. Reciprocal motion can then be applied to one of the linear brushes or to the rotary brushes, in order to bring the entire mechanism into reciprocal motion.